Nothing in paragraph 11 imposes any liability on the Agency with respect to any damage to the extent that it is attributable to any prior defect, want of maintenance or want of repair to the beds or banks of the river or other harbour property or to the act, neglect or default of A.B. Ports, its officers, servants, contractors or agents but the fact that any work or thing has been executed or done in accordance with a plan approved or deemed to be approved by A.B. Ports, or to its satisfaction, or in accordance with a determination under article 54 (arbitration) of the Order, does not (in the absence of negligence on the part of A.B. Ports, its officers, servants, contractors or agents) relieve the Agency from any liability under the provisions of this Schedule.